<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>

    .da{
        width:300px;
        height:300px;
        border:2px solid black;
    }

    .a,.b,.c{
        width:200px;
        height:60px;
    }

    .a{
        background-color:deepskyblue;
    }

    .b{
        background-color: fuchsia;
        position:relative; /*相对定位 相对与自己原来的位置进行移动*/
        top:30px; /*上偏移30像素*/
        left:50px; /*左偏移50像素*/
    }

    .c{
        background-color: gold;
    }
</style>
<body>
    
    <div class="da">
        <div class="a"></div>
        <div class="b"></div>
        <div class="c"></div>
    </div>
</body>
</html>